1. Field of the Invention
An apparatus consistent with the present invention relates to a heat-assisted magnetic recording (“HAMR”) head configured for high-density recording and, more particularly, to a HAMR head that can be fabricated in a monolithic body and realize an enhanced near-field effect.
2. Description of the Related Art
Many studies have been performed in the area of magnetic recording for increasing the magnetic recording density. In the case of longitudinal magnetic recording, a recording density of 100 Gbit/in2 is achieved, and in the case of perpendicular magnetic recording, a recording density more than 100 Gbit/in2 is possible. However, since there is thermal instability in the magnetic recording technology due to the super paramagnetic effect, an increase in the recording density is limited.
The thermal stability of a recording medium is determined by the ratio of magnetic anisotropy energy to thermal energy. In order to increase the magnetic anisotropy energy, the magnetic recording medium must be formed of a material having a high coercive force. When this material is used for magnetic recording, an electric field having an intensity as high as the coercive force should be used. However, since the magnetic field at the tip portion of the recording head is saturated at a predetermined level, the intensity of the magnetic field generated in the magnetic recording head is limited, thereby causing failure in the recording.
To solve the above problem, a HAMR head has been studied. The HAMR head records data by heating a local portion of the recording medium above the Curie temperature and temporarily reducing the coercive force of the local portion. That is, in order to perform a recording operation, the intensity of the required magnetic field can be lowered.
At this point, since a data-recording region is heated above the Curie temperature, the recording density is determined by the width of the heated portion rather than the size of a pole generating the magnetic field in a gap. For example, when light is selected as the heat-assisting medium, the data recording density is determined by the spot size of the light reaching the recording medium. Accordingly, a study on an optical unit that can reduce the spot size of light and increase the intensity of light is required.
FIG. 1 is a perspective view of an example of a conventional HAMR head. Referring to FIG. 1, HAMR head 22 includes a magnetic recording unit, a light source 52 for heating a recording medium 16, and a light transmission module for transmitting the light from the light source 52 to the recording medium 16.
The magnetic recording unit includes a coil 33, which is a magnetic field source, a recording pole 30 for generating a magnetic field for recording, and a return yoke 32 magnetically connected to the recording pole 30 to form a magnetic path H. The recording pole 30 includes first and second layers 46 and 48.
The optical transmission module includes a waveguide 50 for guiding the light emitted from the light source 52 and an optical fiber 54 connecting the light source 52 to the waveguide 50. Optical energy 58 is transmitted to the magnetic recording medium 16 through a heat discharge surface 56 of the waveguide 50, thereby heating a local portion of the magnetic recording medium 16.
The magnetic recording medium 16 moves relative to the HAMR head 22 in a direction indicated by arrow A. Therefore, the heated local portion is located with respect to the recording pole 30 by the relative motion of the magnetic recording medium 16. As a result, the recording pole 30 effectively records data on the local portion whose coercive force is reduced by heating. In addition, after the recording is finished, the heated local portion is cooled down to have the inherent high coercive force, thereby maintaining thermally-stable recording bits.
In order to record at a high density using the HAMR head, the size of the light spot must be sufficiently small while the recording medium must be sufficiently heated. However, the structure of the conventional HAMR head is designed not to provide a field enhancement effect and the waveguide must be independently fabricated from the magnetic head and precisely aligned therewith.